Joint confusion - Bobble head

I'm just cutting my teeth on unity joints :) if I wanted a capsule set on end to be attached to a plane and wobble like a flag pole or more springy, do I put a spring joint on the plane to the capsule, from the capsule to the plane, or just the bottom of the capsule? Or.. do I use a $$anonymous$$nged joint and mess with the spring settings?

Thanks for any help.